The Thread module served as the frontend to the old-style thread model,
called 5005threads,
that was introduced in release 5.005.
That model was deprecated,
and has been removed in version 5.10.

For old code and interim backwards compatibility,
the Thread module has been reworked to function as a frontend for the new interpreter threads (ithreads) model.
However,
some previous functionality is not available.
Further,
the data sharing models between the two thread models are completely different,
and anything to do with data sharing has to be thought differently.
With ithreads,
you must explicitly share() variables between the threads.

You are strongly encouraged to migrate any existing threaded code to the new model (i.e.,
use the threads and threads::shared modules) as soon as possible.

new starts a new thread of execution in the referenced subroutine. The optional list is passed as parameters to the subroutine. Execution continues in both the subroutine and the code after the new call.

Thread-&gt;new returns a thread object representing the newly created thread.

If the variable is locked by another thread, the lock call will block until it's available. lock is recursive, so multiple calls to lock are safe--the variable will remain locked until the outermost lock on the variable goes out of scope.

Locks on variables only affect lock calls--they do not affect normal access to a variable. (Locks on subs are different, and covered in a bit.) If you really, really want locks to block access, then go ahead and tie them to something and manage this yourself. This is done on purpose. While managing access to variables is a good thing, Perl doesn't force you out of its living room...

If a container object, such as a hash or array, is locked, all the elements of that container are not locked. For example, if a thread does a lock @a, any other thread doing a lock($a[12]) won't block.

Finally, lock will traverse up references exactly one level. lock(\$a) is equivalent to lock($a), while lock(\\$a) is not.

async creates a thread to execute the block immediately following it. This block is treated as an anonymous sub, and so must have a semi-colon after the closing brace. Like Thread-&gt;new, async returns a thread object.

The cond_wait function takes a locked variable as a parameter, unlocks the variable, and blocks until another thread does a cond_signal or cond_broadcast for that same locked variable. The variable that cond_wait blocked on is relocked after the cond_wait is satisfied. If there are multiple threads cond_waiting on the same variable, all but one will reblock waiting to reaquire the lock on the variable. (So if you're only using cond_wait for synchronization, give up the lock as soon as possible.)

The cond_signal function takes a locked variable as a parameter and unblocks one thread that's cond_waiting on that variable. If more than one thread is blocked in a cond_wait on that variable, only one (and which one is indeterminate) will be unblocked.

If there are no threads blocked in a cond_wait on the variable, the signal is discarded.

join waits for a thread to end and returns any values the thread exited with. join will block until the thread has ended, though it won't block if the thread has already terminated.

If the thread being joined died, the error it died with will be returned at this time. If you don't want the thread performing the join to die as well, you should either wrap the join in an eval or use the eval thread method instead of join.

detach tells a thread that it is never going to be joined i.e. that all traces of its existence can be removed once it stops running. Errors in detached threads will not be visible anywhere - if you want to catch them, you should use $SIG{__DIE__} or something like that.

The tid method returns the tid of a thread. The tid is a monotonically increasing integer assigned when a thread is created. The main thread of a program will have a tid of zero, while subsequent threads will have tids assigned starting with one.